Free flight arming device



April 26, 1960 J. RABINOW 2,934,020

FREE FLIGHT ARMING DEVICE Original Filed July 5, 1956 2 Sheets-Sheet 1 v \Y I I INVENTOR.

Jacob Eabinum BY April 26; 1960 J. RABINOW 2,934,020

' FREE FLIGHT ARMING DEVICE OriginalFiled July 5, 195a 2 Sheets-Sheet 2 :Eg -7. Y 215( -19 I7 f6- if a 'f 10 gg 72 la is f /f 14 v 0 3 2D 22 INVENTOR. Jan uh R abinmu.

FREE FLIGHT ARMING DEVICE Jacob Rabinow, Prince Georges County, Md., assignor to the United States of America as represented by the Secretary of the Army Original application July 5, 1956, Serial No. 596,118. Divided and this application September 4, 1958, Serial No. 769,274

1 Claim. (Cl. 102-84) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured or used by or for-the Government for governmental purposes without the payment to me of any royalty thereon. This application is a division of application Serial No. 596,118, filed July 5, 1956.

This invention pertains to the art of fuzing projectiles such as bombs, rockets, mortar shells and others. More particularly it relates to safety and arming systems for projectiles. In projectiles of this type, particularly in the case of bombs, the arming cycle of a fuze is usually started by the withdrawal of an arming wire or the charging of a capacitor at the instant of bomb release. Serious accidents have occurred in the past because of the fact that bombs have been accidentally dropped onto airfield runways or decks of aircraft carriers. In such cases the fuzes generally complete their arming cycle even though substantial air travel is normally required. The backwash of propellers or of turbo-jet engines operates arming vanes of such fuzes and duplicates the conditions encountered in proper drops. In some fuzes provision is made to sterilize the fuze if impact occurs before proper arming in order to avoid this disadvantage. This leads to other troubles since such sterilization schemes may result in duds. For example, a bomb may jostle another bomb accidentally immediately after release or a bomb may hit a part of the bomb bay upon its release from the aircraft and thus cause a dud.

To eliminate these disadvantages and to insure much greater safety, the present invention comprises an arming system which makes use of the fact that a bomb or other low velocity projectile in free flight experiences acceleration of less than 1 g. I make use of this fact by a special zero g device so connected that the bomb must be in free flight for several seconds for arming to occur. If the bomb employing this invention should accidentally fall upon the deck of a carrier or upon an airfield runway it would not arm because it then would be under acceleration of 1 g or greater. As described more fully herein, the device can be so arranged that accidental jostling of one bomb by another will not permanently disarm the bomb and proper function will result. This invention of arming a bomb or other projectile under conditions of zero-g or fractional-g may be employed in either electrical or mechanical form.

One'object of this invention, therefore, is an arming system for fuzes adapted to remain inoperative in the event the containing projectile is accidentally dropped upon an airfield runway or aircraft carrier deck.

Another object is an arming system adapted to remain inoperative in the event the fuze is subjected to an acceleration greater than a predetermined amount occurring subsequent to the expiration of a predetermined time.

. A further object is a fuze arming system as aforesaid which will arm even though subjected to an excessively great acceleration provided that acceleration occurs prior to the expiration of a predetermined time interval.

A still further object is a safety device for fuze arming systems adapted to prevent fuze arming in the event the containing missile is accidentally dropped upon an airfield or aircraft carrier runway.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from the following description and accompanying drawings in which:

Figure l is a vertical sectional view of one form of my safety switch in the normal condition.

Figure 2 is a cross sectional view of the device of Fig. 1 taken on the lines 2-2 thereof.

Figure 3 shows the switch of Fig. 1 in the actuated condition.

Figure 4 is a view similar to Fig. 2 showing the switch in the actuated condition.

FigureS is a vertical sectional view of a second form of my switch in the normal condition.

Figure 6 shows the switch of Fig. 5 in the actuated condition.

Figure 7 is a schematic view of an unarmed fuze em-. bodying the arming system of this invention.

Figure 8 is a fragmentary view of Fig. 7 showing the fuze in the armed condition.

Figure 9 is a schematic diagram of the electrical circuitry of the fuze shown in Fig. 7.

Figure 10 is a variation of the circuit of Fig. 9.

Figure 11 is a schematic view of a mechanical switch which is the equivalent of the electrical switch of Fig. 5.

Figure 12 shows the switch of Fig. 11 in the actuated condition.

Referring now to Fig. 1, a metal electrical conductive housing 1 supports an insulating member 2 within the hollow base 2a thereof. Aifixed to member 2 centrally thereof and extending upwardly therefrom is terminal 3. A helical spring 4 has its inner end affixed to terminal 3, the outer end of spring 4 having aflixed thereto a heavy metal ring 5, the ring being concentric with terminal 3 and normally out of contact with all members other than spring 4. Housing 1 is perforated at 1a and 1b to prevent electrical contact between housing 1 and terminal 3.

Fig. 3 shows the contact established between ring 5 and housing 1 when the fuze is under an acceleration of one g or greater acting in a direction upwardly along the surface of the drawing. If one leg of an electrical circuit, not shown in this figure, terminates at housing 1 and the other leg terminates at terminal 3, the circuit will be completed through spring 4 and ring 5 under the condition described.

Figure 4 shows that electrical contact is made under sidewise acceleration (as compared to the upward acceleration of Fig. 3). Ring 5 now contacts the side, rather than the base, of housing 1.

Referring to Fig. 5, a generally cylindrical housing 6 supports an insulating disc 7 which is provided with a cup-like recess 7a in which rests a cylindrical weight 8 axially bored at one end. A tension spring 9 maintains the weight normally in central position by having one end thereof afiixed to disc 7 centrally thereof and the other end afiixed to the closed end of weight 8.

Fig. 6 shows the action which takes place when the assembly of Fig. 5 is accelerated substantially at a right angle to the axis of the weight 8. Spring 9 is extended by the force exerted upon it by weight 8, the weight being permitted to pivot sidewise on its base and in so doing to contact housing 6. Thus, a circuit is completed through spring 9 and weight 8 when terminated at spring 9 and housing 6.

While one device such as shown in Figs. 5 and 6 is omnidirectional, two devices properly connected and placed at right angles to one another will respond to excessive acceleration regardless of the direction of the acceleration.

Referring now to Fig. 7, a fuze ogive 10 has mounted Patented Apr. 26, 1960 upon it a contact ring 11, insulated from the ogive by a suitable member 12, and connected by wiring 13 to a power supply 14, the power supply being grounded to the ogive. Power supply 14, in turn, is connected to an acceleration-sensitive switch 15. The switch 15 may be of a type shown in Figs. 1 or 5. Switch 15 is also connected with the heating element 16 of an explosive motor 16a which, when activated, will cause the expansion of bellows member 16b. The bellows member is so positioned that expansion thereof will cause linear motion of the safety block 17 until that motion is arrested by the stop 18. When such motion has occurred, explosive detonator 19 in aperture 19a of block 17 will be aligned with aperture 20 in safety plate 21, permitting ignition of the booster charge 22 when firing pin 23, which is normally biased forwardly by spring 24, is caused to move rearwardly and engage detonator 19 as a result of impact of pin 23 with a target, not shown. The armed position of explosive motor 16a and block 17 is shown in Figure 8.

The electrical circuitry of the system of Fig. 8 as shown in Fig. 9 employs a capacitor 25, one plate of which is grounded to fuze ogive 10 and the other plate of which is connected with contact ring 11. A second capacitor 26 has one plate connected to ground and the other plate connected through a resistor 27 with contact ring 11. Heating element 16 of explosive motor 16a is connected in series with diode 28 and these two elements are connected in parallel with capacitor 26. Safety switches 29 and 290, which are identical in construction, but whose axes are oriented mutually perpendicular, are connected in parallel and the combination connected in parallel with capacitor 26. A resistor 30 may be connected in series with the switches 29 and 29a.

The circuitry of Fig. 10 is a modification of that shown in Fig. 9. The system of Fig. 10 contains its own power supply 31 which is substituted for capacitor 25 in Fig. 9. Safety device 32, shown here in block form, must be placed in series with power supply 31, such as a battery, to prevent the fuze from becoming energized prematurely. Device 32 may be operated by the conventional arming wire or any other suitable arming device as known to the art. Contact ring 11 is not required when a self-contained power supply is employed inasmuch as the purpose of the ring is to collect a charge from an external source. A resistor may or may not be employed in series with switches 29 and 29a for reasons discussed hereinafter.

Referring again to Fig. 9, as fuze ogive 10 and ring 11 are brought into contact with the terminals of a voltage source, not shown, upon launching, a charge is placed upon capacitor 25. This charge leaks to capacitor 26 through resistor 27 until the striking voltage of diode 28 has been reached. Upon the attainment of such voltage, diode 28 fires, causing current to flow through heating element 16 of explosive motor 16a. If, however, either of the switches 29 or 29a should close before firing of the diode 28 occurs, capacitor 26 will discharge through the switch circuit so completed. The time required for capacitor 26 to assume its initial charge, to discharge through one or the other of switches 29, 29a, and to recharge from capacitor 25 after such discharge, is determined by the values of resistor 27 and capacitor 25, by the voltage on capacitor 25 and by any charge which remains upon capacitor 26 after the switch reopens. The charge which remains upon capacitor 26, for a given capacitor and voltage, is determined by the duration of closure of switches 29 or 2911, up to complete discharge, and by the resistance of the circuit, which may be increased by the addition of a resistor 30 in series with the devices 29 and 2%.

The operation of the circuit of Fig. 10 is identical with the operation of the circuit of Fig. 9 with the exception that power in the Fig. 10 circuit is made available to charge capacitor 26 through resistor 27 from power supply 31 upon actuation of safety device 32 whereas in the Fig. 9 circuit capacitor 26 is charged through resistor 27 from capacitor 25 after capacitor 25 has collected a charge from an external source when the projectile is launched.

Now it can be seen that, should a bomb containing a fuze such as that shown in Fig. 7, strike the bomb bay of the airplane upon being released, a part, at least, of the charge upon capacitor 26 will be discharged through one of the switches 29, 29a, which switch was caused to close under an impact of the bomb with the bomb bay. The amount of charge upon capacitor 26 is small at this time inasmuch as the bomb was released only moments before the impact occurred. Sufficient charge remains upon capacitor 25 to recharge capacitor 26 after the switch reopens after the bomb moves clear of the airplane. Thus, the fuze is in condition to function properly upon impact with a target later in its flight.

If, however, the bomb should fall upon an airfield runway or upon the deck of an aircraft carrier as the plane is ascending or descending, there is a different result. One of the switches 29, 29a will close as before. The charge upon capacitor 26 will discharge through the closed switch as before. This time, however, capacitor 26 will have drawn from capacitor 25 an amount of charge short of that required to fire diode 28 but sufficient to prevent capacitor 25 from recharging capacitor 26 after the switch reopens upon the abatement of acceleration of 1 g or greater. The fuze will, therefore, remain inoperative and safe.

Referring now to Fig. 11, it will be seen that a great similarity exists to the configuration of the device shown in Fig. 5 in that a cylindrical housing 6a is provided with a base 7b having a cup-like recess 70 in which rests a cylindrical weight 8a axially bored at one end. A tension spring 9a, one end of which is affixed to base 7b and the other end of which is afiixed to the closed end of weight 8a, normally maintains the weight in the central position shown in Fig. 11. In his embodiment, however, it is not necessary that the housing 6a or the weight 8a be conductive, nor that the base 7b be non-conductive, inasmuch as this device operates upon mechanical rather than electrical principles. The weight 8a is connected to a lever 33, pivoted at 33a, by means of a motion transmitting linkage 34, such as a cord or cable, threaded through an aperture 38 provided therefor in base 7b. A detent 33b is provided at one end of lever 33 to engage a tooth 35 on balance-wheel 36 of a clock-type arming system, not shown.

In Fig. 12 the device is shown being acted upon by an acceleration of l g or greater directed generally perpendicular to the axis of weight 8a. Weight 811 is driven sidewise by this force and in so doing extends the spring 9a. It also exerts a pull upon linkage 34 which is caused to move to the right of the drawing. Lever 33 is caused to rotate counterclockwise about pivot 33a so that detent 33b engages tooth 35 and arrests the motion of balancewheel 36. In this manner fuze arming is delayed during the time the fuze is subject to an acceleration of at least 1 g.

It will be understood that the embodiments described herein are exemplary only and that other modifications may be made without departing from the spirit'and scope of the invention as set forth in the claim.

What I claim is:

An acceleration responsive safety device for clockwork fuze arming systems having a rotatable, toothed, balance wheel comprising, a cylindrical housing having a base, a cup-shaped weight having the open end thereof normally resting upon said base, a tension spring enclosed within said cup-shaped weight having one end fixed to said base and the other end fixed to said weight remote from said base, said weight being pivotable on said base against the tension of said spring when the device is subjected to an acceleration acting transversely of the weight, a lever pivoted intermediate its ends to saiddevice, a detent on to the other end of said lever and to said weight, whereby pivoting of said weight in response to acceleration pivots said lever to engage said detent with the toothed balance 5 2,863,393

wheel.

References Cited in the file of this patent UNITED STATES PATENTS 2,149,470 Schenk Mar. 7, 1939 6 Middlerniss Apr. 16, 1946 Wandrey July 12, 1949 Gleason June 23, 1953 Leroy Jan. 11, 1955 Sheeley Dec. 9, 1958 

